Theres oil on my spark plugs at the end and i know its not my valve cover gaskets. this is a new rebuilt motor with mods and im pretty sure its a stock head gasket. can anyone help me out?

it doesn't make since i just got it rebuilt and yes it was properly broken in after being rebuilt. so what could cause this problem? its only on cylinders 3 and 4

theres also white smoke coming out of my exhaust and lots of low end power loss .
the oil isnt dried it is wet on the end of the spark plug inside the combustion chamber

i already did a compression test so i know its not the head gasket. how would you know if it was a valve seal leak?